1. Field of the Invention
The invention relates to a device for the protection of the legs of a vehicle occupant in the event of a frontal impact of the vehicle.
2. Description of Related Art
In the event of a frontal impact of a vehicle, for example, a motor vehicle, it is necessary to provide a device for the protection of the vehicle occupants that absorbs the impact energy of the knees and the legs.
For this purpose, it is known to provide deformation elements made of steel, aluminium or plastic foam between a central frame part or central tube, which runs in the transverse direction in the vehicle, and the knee and leg area of the vehicle occupants, in particular, the vehicle occupants on the front seat. The deformation elements are arranged such that they are located directly in front of the knees of a vehicle occupant when the latter has assumed his/her ideal sitting position. Such a deformation element is known from Published German Patent Application DE 10 060 636 A1, and comprises a honeycombed hollow body with a tension strap.
For the purpose of checking the vehicle safety, the sitting position of the vehicle occupant is rigidly prescribed in the corresponding vehicle regulations, but each person in fact assumes a different sitting position, so that the position of the knees in the available foot room varies in the transverse direction of the vehicle. On account of the different body sizes of the vehicle occupants, this position also varies in the height direction. Bent or stretched legs, furthermore, lead to different movement directions of the knees in the event of a vehicle impact. Evaluations of crash tests have shown that the path of the knee at the outset can be described as being virtually circular about the ankle joint.
In the event of an impact, there is the problem that more and more components become deformed with increasing intrusion of the legs and the knees of the vehicle occupants into the dashboard on the driver's side and into the glove box on the front-seat passenger side, as a result of which additional forces are built up.
However, as is shown in FIG. 6, the use of known honeycomb deformation elements leads to a force curve that results from the fact that the known deformation elements work like pressure springs arranged one behind the other. As a result, different force levels arise in the force curve, but they are always increasing. Accordingly, in order not to exceed the biomechanical limiting values in the event of an impact when more and more components are becoming deformed, a reduction of the force level in the force curve of the deformation elements is desired.
Since the known deformation elements have a prescribed deformation direction, reductions in the protective effect can occur in the event of deviations of the load direction from this prescribed deformation direction due to bending of the deformation elements in the transverse direction and in the height direction.
The known deformation elements, moreover, are disadvantageous inasmuch as they comprise extruded profiles which are associated with high costs, and their arrangement in the knee area greatly restricts the installation space available for other components, for example, the glove box on the front-seat passenger side or the vehicle electronics on the driver's side.